The average global temperature has been steadily increasing for more than a century, particularly since the 1950s. In Earth's long history there have been many such periods of global warming, often followed by centuries of cold. Scientists hypothesize that sunspot cycles may contribute to these cyclical changes in global temperature. Many scientists suspect, however, that human activity may be significantly contributing to global warming in modern times.
Our planet would be as cold as the moon except for the insulating effects of certain gases- called greenhouse gases-such as water vapor, carbon dioxide(CO2), methane, and nitrous oxide in the atmosphere. The chemical bonds in carbon dioxide molecule absorb solar energy as heat radiates from Earth. The process called the greenhouse effect, traps heat within the atmosphere in the same way glass traps heat within a green house. There has been a large increase in carbon dioxide in the Earth's atmosphere in recent times. This increase seems to be related to the burning of fossil fuels that has accompanied clearing of the forests and urban industrialization.
The question is: is Global Warming occurring? The correlation of increasing temperatures with increasing carbon dioxide levels is very close. Therefore, many scientists are convinced temperature and carbon dioxide are related. In science, however, correlation does not prove cause and effect. Both global temperature and levels of green house gases may be changing because of other variables that have not been recognized yet. Some countries take seriously the possibility that increasing green house gases play a role in global warming. These countries are attempting to formulate international treaties that place limits on greenhouse-gas emissions. The matter remains controversial, however, and the role of green house gases in global warming is hostly contested.
Examples of ozone depletion or global warming occur on a large scale. But what about serious environmental problems that occur in our own backyard? For example, one important urban environmental problem is chemical pollution. Until recently, people assumed that the environment can absorb any amount of pollution.
By 1985, the scientific community had learned that CFCs are the primary cause of the of the ozone hole . High in the atmosphere, ultraviolet radiation from the sun is able to break the usually stable bonds in CFCs. The resulting free chlorine atoms then enter into series of reactions have been banned as aerosol propellants in spray cans in the United States. Today many countries limit or ban the use of CFCS.
Scientists expect an increased incidence of diseases caused by exposure to ultra violet radiation, because the decrease in ozone allows more ultraviolet radiation to reach the earths surface. These diseases include skin cancer, cataracts(a disorder in which the lens of the eye becomes cloudy), and cancer of the retina, the light-sensitive part of the eye. In fact, in the United States, the number of cases of malignant melanoma, a potentially lethal form of skin cancer, has almost doubled since 1980.
Another source of global warming is coal- burning power plants which sends smoke high into the atmosphere through tall smokestacks, often more than 300m(984ft) tall. This smoke contains high concentrations of sulfur because the coal that plants burn is in sulfur. Scientists have since discovered that the sulfur introduced into the atmosphere by smokestacks can combine with water vapor to produce sulfuric acid back to Earth's surface. In short, these consequences are all related to global warming.
Environmental problems such as global warming affect all inhabitants of an ecosystem without regard to state or national boundaries. As human activities continue to place severe stress on ecosystems, worldwide attention must be focused in solving these problems. Serious attempts to address the overall problem of pollution, the major cause of global warming, have brought about more fundamental changes in our society.
Two effective approaches have been taken to reduce pollution in the United States. The first approach has been to pass laws forbidden it. In the last 30 years, laws have begun to significantly low the spread of pollution. These laws impose strict standard for what can be released into the environment. For example, all cars are required to have catalytic converters to reduce emissions. Similarly, the clean Act of 1990 requires scrubbers on the smokestacks of power plants. converters and scrubbers make cars and energy more expensive. The effect is that the consumer pays more to avoid pulling the environment.
A second effective approach to reducing pollution has been to make it more expensive by placing a tax on it. The gasoline tax is a good example of such a tax. To be fully effective, however, a tax must be high enough to reflect the actual cos of the pollution. By adjusting the tax, the governments attempts to balance the conflicting demands of environmental safety and economic growth. Such taxes often imposed on the industry in the form of "pollution permits," are becoming increasingly common.
In conclusion, we cannot hope to preserve what we do not understand. Human rely on the Earth's ecosystems for food and all the other materials that our civilization depends on. It has been said that we do not inherit the Earth from our parents but borrow it from our children. Therefore, we must preserve for them a world in which they can live. Although solving the world's environmental problem will take the efforts of many people, including politicians, economists, and engineers, the issues are largely biological. When all is said and done, your knowledge of ecology is the essential tool that you can contribute that you can contribute to the effort.
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